Differences In Rate Of Development Research Articles

Mitochondrial content and gene expression profiles in oocyte-derived embryos of cattle selected on the basis of brilliant cresyl blue staining

The aim of this study was to investigate the developmental rate, lipid and mitochondrial distribution and gene expression in oocyte-derived embryos selected on the basis of brilliant cresyl blue (BCB) staining. Lipid content and mitochondrial distribution in Day 8 blastocysts were evaluated by fluorescence intensity, while gene expression was analyzed by real-time PCR. The proportion of blastocysts (30.9%) was greater (P<0.05) in BCB+ than in BCB− oocytes (13%) but not different (P>0.05) from the control group (28.2%). Total cell number was also greater in BCB+ (155.1±36.2) than in BCB− (116.6±40.5) and control (127.5±35.7) blastocysts. Furthermore, the apoptotic cell number was less in BCB+ (3.7±4.4) than in BCB− blastocysts (8.7±8.7) but not different from the control group (5.9±3.9). BCB+ embryos contained more mitochondria compared to BCB− embryos (P<0.05). There was no significant difference in intercellular lipid accumulation in embryos from all groups. Interferon-τ (IFNτ), transforming growth factor β1 (TGFB1) and secreted seminal-vesicle Ly-6 protein 1 (SSLP1) gene expression was greater in BCB+ than in BCB− blastocysts. By contrast, Bcl2-associated X protein (BAX) and heterogeneous nuclear ribonucleoprotein A2/B1 (HNRNPA2B1) gene expression was greater in BCB− than in BCB+ and control embryos. In conclusion, oocyte-derived embryos selected on the basis of BCB staining showed differences in developmental rate, quality, mitochondrial content and target gene expression compared to control embryos.

Effect of Fluctuating Temperatures on the Development of a Forensically Important Blow Fly,Protophormia terraenovae(Diptera: Calliphoridae)

Experiments were conducted to compare the immature development of Protophormia terraenovae (Robineau-Desvoidy) at fluctuating temperatures of 4-28 and 9-23 °C to their mean constant temperature, 16 °C. Overall development was fastest at the greater fluctuation and slowest at the constant temperature but showed similar percentages of development time in each stage. The rate summation effect is suspected to have caused this difference in development rate because fluctuations above the mean increase the rate relatively more than temperatures below the mean can lower the rate.

Erratum to: 264 EXOGENOUS LINOLENIC ACID IN OOCYTE MATURATION MEDIA PROMOTES NUCLEAR MATURATION AND PARTHENOGENETIC PREIMPLANTATION EMBRYONIC DEVELOPMENT IN THE GOAT

Dietary intakes of polyunsaturated fatty acids are thought to mediate a wide range of actions in reproductive tissues. This includes the effects on ovarian follicle and corpus luteum functions via improved energy efficiency as well as providing precursors for the synthesis of signalling molecules such as steroids and prostaglandins. An appropriate level of α-linolenic acid (ALA) in the oocyte maturation medium has been shown to induce molecular changes associated with oocyte maturation and embryo developmental competence. In that light, we hypothesised that supplementation of exogenous ALA to maturation media could enhance nuclear maturation and embryonic development in the goat. A preliminary experiment was executed to measure the level of ALA in antral follicles by gas chromatography/mass spectrometry analysis. Our results revealed that the concentration of ALA in follicular fluids ranged from 0.006 to 0.02 mg mL–1 (21.5 to 71.8 µM, with a mean of ~50 µM). To test the effect of ALA on the competence of goat oocytes to complete meiotic maturation to metaphase II and sustain embryonic development, ovaries were obtained from a local abattoir. Cumulus–oocyte complexes were recovered by the slicing method followed by selection of oocytes with a homogenous cytoplasm and at least three layers of compact cumulus cells. The cumulus–oocyte complexes were placed in maturation media supplemented with 50 µM ALA. Oocytes in the control group were incubated in the same maturation medium without ALA. In vitro maturation (IVM) was performed in a humidified atmosphere containing 5% CO2, 5% O2, and 90% N2 at 38.5°C for 24 h. After IVM, several oocytes from the treatment (n = 170) and control (n = 166) groups were stained with Hoechst and were evaluated in relation to their metaphase-II rate. Other groups of oocytes from both the treatment (n = 70) and control (n = 61) groups were subjected to parthenogenetic activation by applying 1 min of exposure to 2.5 µM ionomycin followed by 2 mM 6-DMAP treatment for 3 h. After activation, oocytes were cultured in CR1aa medium for 7 days under the conditions stated above. Four replications were performed. Differences in developmental rates were analysed for significance by one-way ANOVA using SAS version 8.0 (SAS Institute Inc., Cary, NC, USA), considering P &lt; 0.05 to be significant. As a result, supplementation of the maturation media with ALA did not appear to affect cumulus expansion. In contrast, IVM of goat oocytes in the presence of ALA resulted in a significantly higher maturation rate compared with maturation without ALA supplementation (66.4% v. 57.9%). Likewise, addition of ALA to the IVM medium significantly increased the rate of cleavage (60.1% v. 52.4%) and blastocyst formation (22.6% v. 14.9%), calculated from the activated oocytes. Collectively, the results of our study show that supplementation of IVM media with 50 µM ALA promotes nuclear maturation, increases cleavage rate, and results in higher blastocyst rate in goat oocytes after parthenogenetic activation. Thus, providing appropriate levels of ALA in maturation media could have beneficial effects on embryo development and reproductive efficiency in the goat.

92 DOES THE SEX OF THE EMBRYO AFFECT DEVELOPMENTAL AND APOPTOTIC RATES AT THE BLASTOCYST STAGE?

Several studies have demonstrated differences in developmental rates and metabolism between bovine female and male embryos after IVF. Such differences seem related to the activity of both X chromosomes in female embryos up to the blastocyst stage and can lead to a shift in sex ratio. Developmental differences between male and female embryos are influenced by culture conditions. The objective of this study was to evaluate developmental and apoptotic rates of male and female bovine embryos in 2 SOF-based culture media, one with 5% FCS and the other with 4 mg mL–1 of BSA. Sex-sorted semen of one bull was used to produce cohorts of embryos of the desired sex. In preliminary experiments, IVF procedures were adapted to the use of sexed semen, and the purity of the sexed semen was verified through embryo sexing. The levels of apoptosis were assessed in Day-7 blastocysts using 2 techniques on the same embryos: TUNEL and detection of cleaved caspase-3 by immunostaining (caspase staining). Analysis by confocal microscopy and subsequent 3-D reconstruction allowed a precise cell count. A higher blastocyst rate on cleaved embryos was observed at Day 8 post-insemination for male than for female embryos in both media (BSA: male: 36.7 ± 4.0%, female: 28.6 ± 3.7%; FCS: male: 41.7 ± 2.9%, female: 31.7 ± 4.7%; ANOVA 3, P = 0.01). No significant difference in cell number was observed between male and female blastocysts (BSA: male: 188 ± 9, female: 170 ± 9; FCS: male: 186 ± 6, female: 177 ± 7; ANOVA 3, P = 0.14). In both media a higher proportion of cells showing caspase staining was observed in female than in male embryos (BSA: male: 7.3 ± 1.3%, female: 9.4 ± 2.1%; FCS: male: 9.2 ± 0.6%, female: 14.2 ± 1%; ANOVA 3, P = 0.01), whereas the proportion of stained cells was higher in FCS than in BSA medium whatever the sex (ANOVA 3, P = 0.02). The same tendency, although not significant, was obtained for the proportion of cells showing TUNEL staining with higher values in female than in male embryos (BSA: male: 9.3±2.1%, female: 10.5 ± 2.6%; FCS: male: 13.1 ± 0.9%, female: 16.5 ± 1.1%; ANOVA 3, P = 0.07) and higher values in FCS than in BSA medium whatever the sex (ANOVA 3, P = 0.05). A tendency for a higher proportion of double-stained cells (TUNEL and caspase-positive) was also observed in female embryos whatever the medium (BSA: male: 3.8 ± 1.1%, female: 5 ± 1.6%; SOF: male: 4.8 ± 0.5%, female: 7.0 ± 0.7%; ANOVA 3, P = 0.08). Intriguingly, only about half of the stained cells showed the double staining (TUNEL and caspase). This could be explained by the fact that caspase-3 activation can appear before DNA fragmentation during the apoptosis process and caspase staining disappear when TUNEL staining is still visible. But both caspase-3 activation and DNA fragmentation can also occur independently of apoptosis. In conclusion, male embryos seem to show a higher developmental rate in both media and could be less affected by apoptosis than female ones, particularly when cultured with FCS. Those experiments have to be repeated with the sexed sperm of another bull to draw final conclusions.

Erratum to: 264 EXOGENOUS LINOLENIC ACID IN OOCYTE MATURATION MEDIA PROMOTES NUCLEAR MATURATION AND PARTHENOGENETIC PREIMPLANTATION EMBRYONIC DEVELOPMENT IN THE GOAT

Dietary intakes of polyunsaturated fatty acids are thought to mediate a wide range of actions in reproductive tissues. This includes the effects on ovarian follicle and corpus luteum functions via improved energy efficiency as well as providing precursors for the synthesis of signalling molecules such as steroids and prostaglandins. An appropriate level of α-linolenic acid (ALA) in the oocyte maturation medium has been shown to induce molecular changes associated with oocyte maturation and embryo developmental competence. In that light, we hypothesised that supplementation of exogenous ALA to maturation media could enhance nuclear maturation and embryonic development in the goat. A preliminary experiment was executed to measure the level of ALA in antral follicles by gas chromatography/mass spectrometry analysis. Our results revealed that the concentration of ALA in follicular fluids ranged from 0.006 to 0.02mgmL–1 (21.5 to 71.8µM, with a mean of ~50µM). To test the effect of ALA on the competence of goat oocytes to complete meiotic maturation to metaphase II and sustain embryonic development, ovaries were obtained from a local abattoir. Cumulus–oocyte complexes were recovered by the slicing method followed by selection of oocytes with a homogenous cytoplasm and at least three layers of compact cumulus cells. The cumulus–oocyte complexes were placed in maturation media supplemented with 50µM ALA. Oocytes in the control group were incubated in the same maturation medium without ALA. In vitro maturation (IVM) was performed in a humidified atmosphere containing 5% CO2, 5% O2, and 90% N2 at 38.5°C for 24h. After IVM, several oocytes from the treatment (n=170) and control (n=166) groups were stained with Hoechst and were evaluated in relation to their metaphase-II rate. Other groups of oocytes from both the treatment (n=70) and control (n=61) groups were subjected to parthenogenetic activation by applying 1min of exposure to 2.5µM ionomycin followed by 2mM 6-DMAP treatment for 3h. After activation, oocytes were cultured in CR1aa medium for 7 days under the conditions stated above. Four replications were performed. Differences in developmental rates were analysed for significance by one-way ANOVA using SAS version 8.0 (SAS Institute Inc., Cary, NC, USA), considering P&amp;lt;0.05 to be significant. As a result, supplementation of the maturation media with ALA did not appear to affect cumulus expansion. In contrast, IVM of goat oocytes in the presence of ALA resulted in a significantly higher maturation rate compared with maturation without ALA supplementation (66.4% v. 57.9%). Likewise, addition of ALA to the IVM medium significantly increased the rate of cleavage (60.1% v. 52.4%) and blastocyst formation (22.6% v. 14.9%), calculated from the activated oocytes. Collectively, the results of our study show that supplementation of IVM media with 50µM ALA promotes nuclear maturation, increases cleavage rate, and results in higher blastocyst rate in goat oocytes after parthenogenetic activation. Thus, providing appropriate levels of ALA in maturation media could have beneficial effects on embryo development and reproductive efficiency in the goat.

Will climate change, genetic and demographic variation or rat predation pose the greatest risk for persistence of an altitudinally distributed island endemic?

Species endemic to mountains on oceanic islands are subject to a number of existing threats (in particular, invasive species) along with the impacts of a rapidly changing climate. The Lord Howe Island endemic palm Hedyscepe canterburyana is restricted to two mountains above 300 m altitude. Predation by the introduced Black Rat (Rattus rattus) is known to significantly reduce seedling recruitment. We examined the variation in Hedyscepe in terms of genetic variation, morphology, reproductive output and demographic structure, across an altitudinal gradient. We used demographic data to model population persistence under climate change predictions of upward range contraction incorporating long-term climatic records for Lord Howe Island. We also accounted for alternative levels of rat predation into the model to reflect management options for control. We found that Lord Howe Island is getting warmer and drier and quantified the degree of temperature change with altitude (0.9 °C per 100 m). For H. canterburyana, differences in development rates, population structure, reproductive output and population growth rate were identified between altitudes. In contrast, genetic variation was high and did not vary with altitude. There is no evidence of an upward range contraction as was predicted and recruitment was greatest at lower altitudes. Our models predicted slow population decline in the species and that the highest altitude populations are under greatest threat of extinction. Removal of rat predation would significantly enhance future persistence of this species.

Theory of mind: beyond the preschool years

This is the first book to provide a comprehensive review of the burgeoning literature on theory of mind (TOM) after the preschool years and the first to integrate this literature with other approaches to the study of social understanding. By highlighting the relationship between early and later developments, the book provides readers with a greater understanding of what we know and what we still need to know about higher-order TOM. Although the focus is on development in typical populations, development in individuals with autism and in older adults is also explored to give readers a deeper understanding of possible problems in development. Examining the later developments of TOM gives readers a greater understanding of: Developments that occur after the age of 5. Individual differences in rate of development and atypical development and the effects of those differences. The differences in rate of mastery which become more marked, and therefore more informative, with increased age. What it means to have a “good theory of mind.” The differences between first- and second- order theory of mind development in preschoolers, older children, adolescents, and adults. The range of beliefs available to children at various ages, providing a fuller picture of what is meant by “understanding of belief.” After the introduction, the literature on first-order developments during the preschool period is summarized to serve as a backdrop for understanding more advanced developments. Chapter 3 is devoted to the second-order false belief task. Chapters 4 and 5 introduce a variety of other measures for understanding higher-level forms of TOM thereby providing readers with greater insight into other cognitive and social developmental outcomes. Chapter 6 discusses the relation between children’s TOM abilities and other aspects of their development. Chapters 7 and 8 place the work in a historical context. First, the research on the development of social and mental worlds that predated the emergence of TOM is examined. Chapter 8 then provides a comparative treatment of the two literatures and how they complement one another. Ideal as a supplement in graduate or advanced undergraduate courses in theory of mind, cognitive development, or social development taught in psychology and education. Veteran researchers will also appreciate this book‘s unique synthesis of this critical research.

Comparisons of Life-History Characteristics of a Genetic Sexing Strain With Laboratory Strains ofAnopheles arabiensis(Diptera: Culicidae) From Northern Sudan

A genetic sex separation strain (GSS) has been created for Anopheles arabiensis (Patton) (Diptera: Culicidae), one of the major African malaria vectors, for use in controlling wild populations of this species via the sterile insect technique (SIT). This GSS strain, "ANO IPCL1," allows sex separation by a translocation linking a dieldrin resistance allele and the Y chromosome. Differences between ANO IPCL1 relative to wild strains might reflect its field performance and therefore are of concern. Of more immediate interest is how differences might affect production during mass rearing. Life-history parameters were measured for the ANO IPCL1 strain and the two wild strains from which it originated. Although developmental rate differences were found among them, none were large. However, a major observed variation was the very low intrinsic fertility of ANO IPCL1 because of the translocation itself. This resulted in a much lower rate of increase: ANO IPCL1 was able to double its population size, in 7.8 +/- 0.4 d, whereas Dongola and Sennar strains could do so in 4.9 +/- 0.5 and 5.6 +/- 0.4 d. The presence of the Y-autosome translocation mainly affected the natural fertility of the males, and this will require amplification steps during mass rearing.

Incentive Motivation, Cognitive Control, and the Adolescent Brain: Is It Time for a Paradigm Shift?

It can be argued that adolescents' decision making is biased more by motivational factors than by cognitively driven calculations of outcome probabilities. Brain-based models, derived from structural and functional neuroimaging perspectives to account for this bias, have focused on purported differences in rates of development of motivational and regulatory-control systems. This article proposes a neurochemically based framework for understanding adolescents' behavioral biases_and suggests that there should be an increased focus on the dopaminergic substrates of incentive motivation, which increases into adolescence and decreases thereafter. The article also discusses the manner in which this increase interacts with executive control systems in affecting self-regulation.

Potential use of the fungus Beauveria bassiana against the western flower thrips Frankliniella occidentalis without reducing the effectiveness of its natural predator Orius sauteri (Hemiptera: Anthocoridae)

Orius sauteri (Poppius; Hemiptera: Anthocoridae) is an important predator of western flower thrips, Frankliniella occidentalis (Pergande; Thysanoptera: Thripidae). O. sauteri would be directly exposed to the entomopathogenic fungus Beauveria bassiana (Bals.) Vuillemin in the field should the fungus be used as a biopesticide. If the fungus were to negatively affect O. sauteri in agro-ecosystems, predation of F. occidentalis by O. sauteri may be limited. The present study was undertaken to evaluate the insecticidal activity of strain B.bassiana-RSB of B. bassiana, which is highly virulent to F. occidentalis, on the predator under laboratory conditions. Results showed that, regardless of the concentration applied to first instars, Bb-RSB was not insecticidal against O. sauteri, nor did direct applications affect the developmental rate of the predator. Significant differences in developmental rates and adult longevity were observed between O. sauteri that fed on Bb-RSB-infected F. occidentalis cadavers and those that fed on untreated thrips. Developmental time (from first instar to adult) increased from 0.3 to 0.7 days and adult longevity decreased by 0.8 to 1.2 days for predators fed thrips treated with low and high concentrations of strain Bb-RSB, respectively, compared with predators fed on untreated thrips. However, these differences were only 3–13% of mean values for the controls, suggesting that the effects of Bb-RSB on O. sauteri are relatively minor. These findings highlight the potential use of O. sauteri in combination with B. bassiana for the biocontrol of F. occidentalis, but field tests must be performed to confirm their compatible use.

The developmental trajectory of leaflet morphology in wild tomato species.

Leaves between species vary in their size, serration, complexity, and shape. However, phylogeny is not the only predictor of leaf morphology. The shape of a leaf is the result of intricate developmental processes, including heteroblastic progression (changes in leaf size and shape at different nodes) and the developmental stage of an organ. The leaflets that arise from complex leaves are additionally modified by their positioning along the proximal-distal axis of a leaf and whether they fall on the left or right side of leaves. Even further, leaves are environmentally responsive, and their final shape is influenced by environmental inputs. Here, we comprehensively describe differences in leaflet shape between wild tomato (Solanum section Lycopersicon) species using a principal component analysis on elliptical Fourier descriptors arising from >11,000 sampled leaflets. We leverage differences in developmental rate to approximate a developmental series, which allows us to resolve the confounding differences in intrinsic leaflet form and developmental stage along positions of the heteroblastic leaf series and proximal-distal axis of leaves. We find that the resulting developmental trajectory of organs at different positions along these axes are useful for describing the changes in leaflet shape that occur during the shade avoidance response in tomato. We argue that it is the developmental trajectory, the changes in shape that occur over developmental time in organs reiterated at multiple positions, that is the relevant phenotype for discerning differences between populations and species, and to understand the underlying developmental processes that change during evolution.

Northern natterjack toads (Bufo calamita) select breeding habitats that promote rapid development

It is generally believed that harsh climate inhibits growth and development of ectotherms at high latitudes. However, this environmental effect may be counterbalanced by countergradient genetic variation and habitat selection. While there is laboratory evidence for genetically based increases in growth and development rates in amphibians living at high latitudes, it remains unclear how environmental and genetic effects combine in the field to produce gradients of phenotypic variation. We performed a field study on the growth and development of tadpoles and habitat selection of breeding adults of the natterjack toad (Bufo calamita) in Denmark and in Estonia where the average onset of breeding differs by 12 days. Although growth and development of Estonian tadpoles trailed Danish conspecifics during the first half of the larval period, Estonian tadpoles caught up in both body length and developmental stage to Danish tadpoles in the last third of the larval period. Breeding ponds in Denmark were significantly larger and deeper than in Estonia, however, the water temperatures in the ponds did not vary substantially between the countries. In Estonia the toads selected shallower breeding ponds with higher temperature and oxygen concentrations, suggesting, that at higher latitudes active selection of specific water bodies ensures faster growth and development of larvae. The results, together with previous laboratory evidence, indicate that amphibian distribution limits are shaped both by adaptive differences in developmental rates and behavioural plasticity. To cope with harsh climates, amphibians in the north apparently require shallow water bodies — a habitat particularly vulnerable to anthropogenic degradation.

Embryonic communication in the nest: metabolic responses of reptilian embryos to developmental rates of siblings

Incubation temperature affects developmental rates and defines many phenotypes and fitness characteristics of reptilian embryos. In turtles, eggs are deposited in layers within the nest, such that thermal gradients create independent developmental conditions for each egg. Despite differences in developmental rate, several studies have revealed unexpected synchronicity in hatching, however, the mechanisms through which synchrony are achieved may be different between species. Here, we examine the phenomenon of synchronous hatching in turtles by assessing proximate mechanisms in an Australian freshwater turtle (Emydura macquarii). We tested whether embryos hatch prematurely or developmentally compensate in response to more advanced embryos in a clutch. We established developmental asynchrony within a clutch of turtle eggs and assessed both metabolic and heart rates throughout incubation in constant and fluctuating temperatures. Turtles appeared to hatch at similar developmental stages, with less-developed embryos in experimental groups responding to the presence of more developed eggs in a clutch by increasing both metabolic and heart rates. Early hatching did not appear to reduce neuromuscular ability at hatching. These results support developmental adjustment mechanisms of the 'catch-up hypothesis' for synchronous hatching in E. macquarii and implies some level of embryo-embryo communication. The group environment of a nest strongly supports the development of adaptive communication mechanisms between siblings and the evolution of environmentally cued hatching.

Longitudinal Development of Cortical and Subcortical Gray Matter from Birth to 2 Years

Very little is known about cortical development in the first years of life, a time of rapid cognitive development and risk for neurodevelopmental disorders. We studied regional cortical and subcortical gray matter volume growth in a group of 72 children who underwent magnetic resonance scanning after birth and at ages 1 and 2 years using a novel longitudinal registration/parcellation approach. Overall, cortical gray matter volumes increased substantially (106%) in the first year of life and less so in the second year (18%). We found marked regional differences in developmental rates, with primary motor and sensory cortices growing slower in the first year of life with association cortices growing more rapidly. In the second year of life, primary sensory regions continued to grow more slowly, while frontal and parietal regions developed relatively more quickly. The hippocampus grew less than other subcortical structures such as the amygdala and thalamus in the first year of life. It is likely that these patterns of regional gray matter growth reflect maturation and development of underlying function, as they are consistent with cognitive and functional development in the first years of life.

Testing the role of phenotypic plasticity for local adaptation: growth and development in time-constrained Rana temporaria populations

Phenotypic plasticity can be important for local adaptation, because it enables individuals to survive in a novel environment until genetic changes have been accumulated by genetic accommodation. By analysing the relationship between development rate and growth rate, it can be determined whether plasticity in life-history traits is caused by changed physiology or behaviour. We extended this to examine whether plasticity had been aiding local adaptation, by investigating whether the plastic response had been fixed in locally adapted populations. Tadpoles from island populations of Rana temporaria, locally adapted to different pool-drying regimes, were monitored in a common garden. Individual differences in development rate were caused by different foraging efficiency. However, developmental plasticity was physiologically mediated by trading off growth against development rate. Surprisingly, plasticity has not aided local adaptation to time-stressed environments, because local adaptation was not caused by genetic assimilation but on selection on the standing genetic variation in development time.

Response of a red clone of Myzus persicae (Hemiptera: Aphididae) to sublethal concentrations of imidacloprid in the laboratory and greenhouse

Pest resurgence following a pesticide application may occur owing to a stimulatory (hormetic) response to sublethal insecticide concentrations. The objective of the present study was to examine the potential for a greenhouse-derived red clone of Myzus persicae to exhibit resurgence owing to a hormetic response following a systemic imidacloprid treatment in a bell pepper greenhouse. No differences in mortality and fecundity were observed among apterous adults exposed to sublethal imidacloprid concentrations on excised pepper leaves fed aqueous solutions of imidacloprid. Survival of first-generation progeny was negatively affected by imidacloprid exposure, yet surviving progeny exhibited no differences in development rates or fecundity from progeny of adults unexposed to imidacloprid. Aphid mortality declined most rapidly in clip cages on pepper leaves at the top of the pepper canopy as compared with leaves present at the middle or bottom of the pepper canopy. Imidacloprid decays rapidly in mature pepper plants, resulting in sublethal concentrations in the upper canopy in as little as 4 weeks. Sublethal insecticide concentrations have been implicated in the resurgence of pest populations; however, exposure to sublethal doses of imidacloprid are unlikely to result in pesticide-induced resurgence of the M. persicae aphid clone examined in this study.

Egg development rates for use in egg production methods (EPMs) and beyond

Egg incubation experiments are the primary source of data for temperature-dependent development models used in the egg production method (EPM) for stock assessments. What at first appears as a relatively simple experiment, to incubate fertilized eggs at a variety of temperatures while recording the time they spend in each stage, proves to be a more complicated exercise. The criteria for these experiments, and considerations of source material, experimental systems, and sources of error are presented, with examples from previous experiments on a variety of species world-wide. The influence of different factors on the statistical models used in EPM is reviewed. To allow more robust generalizations and avoid the limitations of maternal effects a number of different parents and parental crosses should be used. The question of whether to replicate within batches, between batches, or between crosses or even over years is evaluated. Since individual eggs tend to develop at different rates (natural variability) consideration should be given to the use of populations or individual observations. In some species there are important stock specific differences in development rates, as well as differences in stage specific mortality rates. Egg quality (size or composition) also influences development rates in some species. These sources of variation should be incorporated into experiments on temperature-dependent development rates. Stock specific patterns should be considered before applying development rates to stocks that were not used in the original model formulation. Good quality experimental data on egg development rates are valuable for many applications in addition to EPM assessments, and the quality criteria are equally important for their use in ecosystem and climate modeling.

Effects of Malathion on the Insect Succession and the Development of Chrysomya megacephala (Diptera: Calliphoridae) in the Field and Implications for Estimating Postmortem Interval

A field study on the effects of malathion on insect succession and the development of carrion flies on corpses, and its quantitative determination from the larvae on decomposing rabbit carrion was conducted. The rabbits were treated with malathion at concentrations of lethal, half-lethal and fourth-lethal doses. Malathion altered decomposition rates and species diversity: Chrysomya megacephala (Diptera: Calliphoridae) was the most abundant adult species in all the experiments; third instar larvae of Chrysomya rufifacies (Diptera: Calliphoridae) were not found on the toxic carcasses but were collected from the control; the appearance of beetles on the treated carcass was later by 1 to 3 days than on the control carcass. Development rate of the dominated species C. megacephala larvae and pupae was observed. Stepwise increases in the period of larval development, the maximum length of larvae, and weight of pupae were observed with increasing malathion concentrations. However, there was no significant difference in the duration of the pupal stage. The differences in development rate were sufficient to alter postmortem interval estimates based on larval development by 12 to 36 hours. The time of finding fresh pupae from the fourth-lethal carcass was 12 hours later than the control. Accumulations of the pesticide in larvae were observed, but no correlations were found between larvae concentrations and the initial quantity administered to rabbits.In conclusion, it is necessary to consider the effects of malathion present in decomposing bodies when estimating the postmortem interval based on entomological evidence. The results of this study have more practical implications for forensic investigations because it is under natural conditions.

Nosema pyrausta and Cry1Ab‐incorporated diet led to decreased survival and developmental delays in European corn borer

AbstractThe high dose/refuge strategy for delaying evolution of resistance to Bt maize [Zea mays L. (Poaceae)] relies on random mating between resistant European corn borers, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), and susceptible O. nubilalis from the refuge. However, differences in developmental rate caused by feeding on Bt maize, or infection with the microsporidium Nosema pyrausta Paillot (Microsporida: Nosematidae) may result in assortative mating. Developmental delays and mortality caused by infection with N. pyrausta and feeding on Bt maize were quantified alone and in combination in Cry1Ab‐resistant and susceptible O. nubilalis. Feeding on Cry1Ab‐incorporated diet significantly increased number of days from hatch to pupation and decreased survival in the resistant population. Infection with N. pyrausta increased mortality and lengthened development in both the resistant and susceptible populations. The combination of Cry1Ab‐incorporated diet and infection with N. pyrausta in resistant O. nubilalis lengthened development and increased mortality to a greater extent than either factor alone. Greater larval delays of resistant O. nubilalis feeding on Bt maize could lead to temporal isolation from adults emerging from refuge maize. The resulting assortative mating would hasten the evolution of resistance. Developmental delays caused by infection with N. pyrausta may increase the likelihood of mating between resistant and infected susceptible adults emerging from refuge maize, producing infected offspring that are also more susceptible to Bt maize.

The Endo-siRNA Pathway Is Essential for Robust Development of the Drosophila Embryo

BackgroundRobustness to natural temperature fluctuations is critical to proper development in embryos and to cellular functions in adult organisms. However, mechanisms and pathways which govern temperature compensation remain largely unknown beyond circadian rhythms. Pathways which ensure robustness against temperature fluctuations may appear to be nonessential under favorable, uniform environmental conditions used in conventional laboratory experiments where there is little variation for which to compensate. The endo-siRNA pathway, which produces small double-stranded RNAs in Drosophila, appears to be nonessential for robust development of the embryo under ambient uniform temperature and to be necessary only for viral defense. Embryos lacking a functional endo-siRNA pathway develop into phenotypically normal adults. However, we hypothesized that small RNAs may regulate the embryo's response to temperature, as a ribonucleoprotein complex has been previously shown to mediate mammalian cell response to heat shock.Principal FindingsHere, we show that the genes DICER-2 and ARGONAUTE2, which code for integral protein components of the endo-siRNA pathway, are essential for robust development and temperature compensation in the Drosophila embryo when exposed to temperature perturbations. The regulatory functions of DICER-2 and ARGONAUTE2 were uncovered by using microfluidics to expose developing Drosophila embryos to a temperature step, in which each half of the embryo develops at a different temperature through developmental cycle 14. Under this temperature perturbation, dicer-2 or argonaute2 embryos displayed abnormal segmentation. The abnormalities in segmentation are presumably due to the inability of the embryo to compensate for temperature-induced differences in rate of development and to coordinate developmental timing in the anterior and posterior halves. A deregulation of the length of nuclear division cycles 10–14 is also observed in dicer-2 embryos at high temperatures.ConclusionsResults presented herein uncover a novel function of the endo-siRNA pathway in temperature compensation and cell cycle regulation, and we hypothesize that the endo-siRNA pathway may regulate the degradation of maternal cell cycle regulators. Endo-siRNAs may have a more general role buffering against environmental perturbations in other organisms.